Here is our scenario. New prop shaft, rebuilt and reinstalled stuffing box, re worked prop, new cutlass bearing, and engine
re-aligned to within 0.04" (closest we could get without machining new engine
mounts) and we have a vibration coming from either the prop, shaft, or rudder
. Here is the trick: I recorded the sound while we were at 2000 engine rpm
(about 690 shaft) and the frequency of the vibration is half of shaft rpm
(340-360hz). And it is LOUD! You can feel it in the deck
. The sound is present in forward, and reverse. There are rpm bands where the intensity changes, but it's always there. Frequency stays about 1/2 shaft rpm throughout the range as best I can tell.
The prop clearances all check out, and the vibration is present at all rpm ranges (so we know it's not 'singing').
Here is a recording of the sound (on my Dropbox)
Any suggestions would be of help. We are paying for a haul today to see if there is anything goofy going on, but this is driving us nuts.
Thanks for any suggestions you can send our way!
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